When making deviled eggs, put the yolks in a ziplock or sandwich bag, add your mayo and whatever else you put in them. Mash everything together in the bag, then snip off a corner of the bag and use it to pipe the yolk into the whites. No mess at all!
In that vein, if you make pumpkin (or other types) purée at home, put 1, 2, or 3 cups' worth in appropriately sized freezer ziplocs. Then when you use for baking, thaw and snip one corner and you can squeeze into the mixing bowl very easily. It took me a few times opening the bag via the zipper and causing a mess before I learned this trick. I think I originally read it as an easy way to squeeze pancake mix into neat circles, though I use a pitcher-style mixing bowl for that.
If a recipe calls for an unusual ingredient, at least try it that way once before altering if you don't think it would suit your tastes. I tried a recipe for bacon, mushroom, and onion pasta that listed fresh mint
as an ingredient. It's good without, but the mint, chopped and sprinkled on top, really adds something special. Also the recipe calls for adding salt each time an ingredient is added to the skillet - seemed like a lot but it turns out this is also necessary, without it the dish comes out surprisingly bland. (I do reserve the right to not follow this rule if the recipe calls for Parmesan, which I can't stand and never miss.)